Frost resistance - a neglected driver of plant phenology and distribution?

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The ongoing global climate change is altering the abiotic conditions for life on earth at unprecedented rates which causes significant changes in plant performance and distribution. In general, most plant species adapt to a changing climate, i.e. warmer temperatures, by starting their spring phenology earlier and ending their autumn phenology later, leading to an overall increase in growing-season length. Plant species also move their occurrence to more north-eastern sites or higher elevations to keep the abiotic conditions to which the plant populations are adapted constant. Previous studies have shown that phenological responses and range shifts are very species-specific, and not all plant species can change their phenology and occurrence to equally large extents. It is not clear why some species do change whereas others do not. The changes in phenology and range put plants at risk of late frost events, as these do still occur in a warming climate, and are in general more frequent at higher elevation and latitude. Plant functional traits describe fundamental properties of plants and provide a good insight into their ecological behaviour as well as their performance. In this project, I postulate that frost resistance (FR) is a key trait in functional ecology. The importance of FR has been widely neglected in previous research even though FR is a crucial factor for plant survival and performance, since it is laborious to measure. More specifically, in this project I will test the two overall hypotheses that: 1. A species’ ability to shift its spring phenology to earlier dates is driven by its ability to tolerate late-frost events as shifts without high FR will lead to frost damages. 2. A species’ ability to shift its distributional range towards the northeast and higher elevational sites is driven by its ability to tolerate late-frost events as the likelihood of late-frost events increase with these shifts. In parallel, we will assess the impact of other plant functional traits relating to plant performance, which are already widely measured, to illustrate the impact of FR as compared with other traits of species. I will combine these hypotheses in this project and collect and analyse data from a wide geographical range and along elevational gradients. We shall use previously published data in a meta-analysis and data from a network of Botanical Gardens across the northern hemisphere, where the phenology of herbaceous species is monitored using standardised protocols. These field observations will be complemented by a greenhouse experiment, where a selected abiotic factor (temperature) can be manipulated and plants from different origins observed. Assessing the contribution of FR to the shifts in phenology and to the spatial extent of a species will help us to forecast species’ behaviour under further changes in climate and to fine-tune the predictions of plant community compositions and therefore biodiversity during further climate change.